Two-speed transmission having two clutches

ABSTRACT

A two-speed transmission having two clutches includes an electric motor, a middle shaft, a first clutch, a second clutch, a first gear assembly and a second gear assembly. The electric motor includes a spindle. The first clutch and the second clutch are furnished on the middle shaft coaxially. The first gear assembly and the second gear assembly are coupled to the first clutch and the second clutch through a first shaft portion and a second shaft portion of the middle shaft to generate a first gear ratio and a second gear ratio, respectively. When the first clutch is activated to connect with the first shaft portion, the second clutch separates from the second shaft portion, so that the electric motor outputs a first torque corresponding to the first gear ratio through the first gear assembly. Similarly, the electric motor outputs a second torque corresponding to the second gear ratio.

This application claims the benefit of Taiwan application Serial No.105101238, filed Jan. 15, 2016, the disclosure of which is incorporatedby reference herein in its entirety.

TECHNICAL FIELD

The disclosure relates in general to a transmission having two clutches,and more particularly to a two-speed transmission for an electricvehicle and capable of providing different torques by switching thespeed gears of different gear ratios.

BACKGROUND

As electric vehicle are getting more and more popular, the performanceof a transmission is getting more and more important. Most of existingelectric vehicles adopt one-speed transmission with a constant gearratio of 6.4:1˜7.5:1. Under such circumstance, when the vehicle isdriving up the slope, the one-speed transmission cannot provide a hightorque; and when the vehicle is driving on a flat road, the one-speedtransmission cannot provide a high speed due to the restriction of thetransmission gear ratio.

Since existing one-speed transmissions cannot be effectively used, manyproblems will arise. For example, the climbing capability is poor, thestart-up is energy consuming, and the efficiency is low. When thevehicle is driving down the slope and the speed is accelerated, theelectric motor may be dragged, and to the worse, may even be burnt down.

SUMMARY

The disclosure is directed to a two-speed transmission having twoclutches capable of providing two gear ratios to satisfy the driver'sdifferent requirements of driving the vehicle at a high torque ordriving the vehicle at a high speed respectively. The two-speedtransmission having two clutches has the features of high energyutilization rate and strong climbing capacity.

According to one embodiment, a two-speed transmission having twoclutches including an electric motor, a middle shaft, a first clutch, asecond clutch, a first gear assembly and a second gear assembly isprovided. The electric motor includes a spindle. The first clutch andthe second clutch are furnished on the middle shaft coaxially. The firstgear assembly is coupled to the first clutch through a first shaftportion of the middle shaft to generate a first gear ratio. The secondgear assembly is coupled to the second clutch through a second shaftportion of the middle shaft to generate a second gear ratio differentfrom the first gear ratio. When the first clutch is activated to connectwith the first shaft portion, the second clutch separates from thesecond shaft portion, so that the electric motor outputs a first torquecorresponding to the first gear ratio through the first gear assembly.When the second clutch is activated to connect with the second shaftportion, the first clutch separates from the first shaft portion, sothat the electric motor outputs a second torque corresponding to thesecond gear ratio through the second gear assembly.

The above and other aspects of the disclosure will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment(s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B respectively are an appearance diagram of a two-speedtransmission for an electric vehicle and a cross-sectional view along across-sectional line A-A thereof according to an embodiment of thedisclosure.

FIG. 2 is a schematic diagram of a two-speed transmission for anelectric vehicle according to an embodiment of the disclosure.

FIGS. 3 and 4 respectively are an internal structural diagram of atwo-speed transmission for an electric vehicle and a simplifiedreference diagram thereof according to an embodiment of the disclosure.

FIGS. 5A-5C respectively are operation diagrams of a two-speedtransmission for an electric vehicle according to an embodiment of thedisclosure.

In the following detailed description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

DETAILED DESCRIPTION

In an embodiment of the disclosure, the transmission has two switchableclutches. As one clutch connects with the middle shaft and the otherclutch separates from the middle shaft, different gear ratios can beprovided to meet different requirements of providing a high torque whenthe vehicle is driving up the slope and achieving a high rotation speedwhen the vehicle is driving on a flat road. Thus, the climbingcapability can be improved and the energy utilization rate can beincreased.

In an embodiment, two gears with different gear ratios are respectivelyinstalled on the differential and are controlled by respective clutches.When the first clutch connects with the first shaft portion of themiddle shaft, the second clutch separates from the second shaft portionof the middle shaft. Meanwhile, the rotor of the electric motor drivesthe spindle and the middle shaft to rotate and output a first torquecorresponding to the gear ratio of the first gear assembly through thefirst gear assembly. Then, the first gear assembly is meshed with thedifferential through the output shaft gear to transfer the first torqueto the power output shaft of the vehicle.

Besides, when the first clutch separates from the first shaft portion ofthe middle shaft, the second clutch connects with the second shaftportion of the middle shaft. Meanwhile, the rotor of the electric motordrives the spindle and the middle shaft to rotate and output a secondtorque corresponding to the gear ratio of the second gear assemblythrough the second gear assembly. Then, the second gear assembly ismeshed with the differential through the output shaft gear to transferthe second torque to the power output shaft of the vehicle.

The first torque is a high torque corresponding to the first gearassembly with a high gear ratio under which the vehicle can achieve alow rotation speed but a high torque. The high gear ratio is applicableto the vehicle starting up or driving up or down the slope. The secondtorque is a low torque corresponding to the second gear assembly with alow gear ratio. Under the low gear ratio, the vehicle can achieve a highrotation speed but a low torque. The low gear ratio is applicable to thevehicle driving on a flat road.

A number of embodiments are disclosed below for elaborating thedisclosure. However, the embodiments of the disclosure are for detaileddescriptions only, not for limiting the scope of protection of thedisclosure.

Refer to FIGS. 1˜4. FIGS. 1A and 1B respectively are an appearancediagram of a two-speed transmission 100 for an electric vehicle and across-sectional view along a cross-sectional line A-A thereof accordingto an embodiment of the disclosure. FIG. 2 is a schematic diagram of atwo-speed transmission 100 for an electric vehicle according to anembodiment of the disclosure. FIGS. 3 and 4 respectively are an internalstructural diagram and a simplified reference diagram of a two-speedtransmission 100 for an electric vehicle according to an embodiment ofthe disclosure.

As indicated in FIGS. 1A, 1B and 2, a two-speed transmission 100 for anelectric vehicle includes an electric motor 110, a middle shaft 115, afirst gear assembly 120, a first clutch 125, a second gear assembly 130and a second clutch 135. The electric motor 110 includes a stator 111, arotor 112 and a spindle 113. The stator 111 is fixed on the housing ofthe electric motor 110. The center of the rotor 112 connects with thespindle 113 and drives the spindle 113 to rotate. The spindle 113 canoutput the power of the electric motor 110 to a driving mechanism, suchas the differential 118T and the power output shaft 117 of a vehicle. Inan embodiment, the electronic control unit (ECU) detects vehicle speedand road conditions by using an external sensor. The ECU can switch thetwo-speed transmission 100 for an electric vehicle between a first shiftmode and a second shift mode to adjust the gear ratio of thetransmission, such that the power outputted by the electric motor 110can meet the requirement of providing a high torque or achieving a highrotation speed.

As indicated in FIG. 1A, each of the spindle 113, the middle shaft 115and the power output shaft 117 has two bearings B, such as ballbearings, through which the spindle 113, the middle shaft 115 and thepower output shaft 117 can be firmly installed within the body of thetwo-speed transmission 100 for an electric vehicle.

The first gear assembly 120 includes a first main gear 121 and a firstcounter gear 122, wherein the first main gear 121 is furnished on thefirst shaft portion 115A of the middle shaft 115 and couples to thefirst clutch 125, and the first counter gear 122 is furnished on thedifferential 118T. The first gear assembly 120 can generate a first gearratio.

The second gear assembly 130 includes a second main gear 131 and asecond counter gear 132, wherein the second main gear 131 is furnishedon the second shaft portion 115B of the middle shaft 115, and the secondcounter gear 132 is furnished on the differential 118T and couples tothe second clutch 135. The second gear assembly 130 can generate asecond gear ratio different from the first gear ratio. In an embodiment,a bearing 119, such as a ball bearing is furnished between the firstshaft portion 115A and the second shaft portion 115B of the middle shaft115, such that the first shaft portion 115A and the second shaft portion115B can be rotated coaxially. Additionally, the diameter of the secondshaft portion 115B is larger than the diameter of the first shaftportion 115A, such that the second shaft portion 115B can be mounted onthe first shaft portion 115A, and the actual length of the middle shaft115 can be reduced. However, the disclosure is not limited thereto, andthe second shaft portion 115B can be furnished in a different way.

Moreover, the spindle gear 114 is furnished on the spindle 113, and themiddle shaft gear 116 is furnished on the clutch. The spindle gear 114is meshed with the middle shaft gear 116 to transfer the power of theelectric motor 110.

The first gear assembly 120 outputs the power of the electric motor 110as a first torque, and drives the differential 118T to rotate andtransfer the first torque to the power output shaft 117 of the vehicle.The second gear assembly 130 outputs the power of the electric motor 110as a second torque, and drives the differential 118T to rotate andtransfer the second torque to the power output shaft 117 of the vehicle.In another embodiment, the middle shaft gear 116 and the spindle gear111 are coupled by a belt or other moving parts to output the power.

As disclosed above, two gear assemblies with different gear ratios areused in conjunction with a clutch controller to switch the gears ofdifferent gear ratios and provide different torques to the power outputshaft 117 of the vehicle, such that the different requirements of hightorque or high speed can be satisfied. The gear ratio is a ratio of thenumber of teeth of the output gear to the number of teeth of the inputgear. The first gear ratio, such as between 6˜7, is applicable to thesituation when a high rotation speed is required. The second gear ratio,such as 11˜12, is applicable to the situation when a high torque isrequired. The definition of the first gear ratio and the definition ofthe second gear ration are exchangeable, and the disclosure does nothave specific restrictions to the gear ratio.

Refer to FIGS. 3 and 4. The middle shaft gear 116 is furnished on acommon housing 124 of the first clutch 125 and the second clutch 135,wherein the first clutch 125 and the second clutch 135 can be a set offriction-plate clutches. The first clutch 125 includes a plurality offirst static friction plates 126 furnished on the clutch centeringsleeve 128 and a plurality of first dynamic friction plates 127staggered with the first static friction plates 126 and neighboring withthe first static friction plates 126 to each other. The second clutch135 includes a plurality of second static friction plates 136 furnishedon the clutch centering sleeve 138 and a plurality of second dynamicfriction plates 137 staggered with the second static friction plates 136and neighboring with the second static friction plates 136 to eachother.

The first dynamic friction plates 127 are furnished on the inner-wall ofthe common housing 124, and the first dynamic friction plates 127 matchthe inner spline TS1 furnished on the common housing 124 and extended inan axial direction of the middle shaft 115, such that the first dynamicfriction plates 127 can move on the inner spline TS1 along the axialdirection. The first dynamic friction plates 127 rotate around themiddle shaft 115 through the rotation of the common housing 124. Thefirst static friction plates 126 match the outer spline TS2 furnished onthe clutch centering sleeve 128 and extended along an axial direction ofthe middle shaft 115, such that the first static friction plates 126 canmove on the outer spline TS2 along the axial direction. A first pressuredisc 129 is furnished on the clutch centering sleeve 128. The firstpressure disc 129 can be driven by the hydraulic circuit 140 to movealong an axial direction of the middle shaft 115 (the axial direction isrepresented by arrow signs) and push the first static friction plates126 to tightly connect with the first dynamic friction plates 127.

FIGS. 5A˜5C respectively are operation diagrams of a two-speedtransmission for an electric vehicle according to an embodiment of thedisclosure. Refer to FIG. 5A. When the first piston P1 is pushed on bythe hydraulic circuit 140, the first pressure disc 129 furnished on theclutch centering sleeve 128 is activated by the first piston P1 totightly press the first static friction plates 126 and the first dynamicfriction plates 127, such that the first static friction plates 126 andthe first dynamic friction plates 127 tightly connect with each other.The first static friction plates 126 are furnished on the clutchcentering sleeve 128 which is further coupled to the first shaft portion115A of the middle shaft 115. After the first static friction plates 126and the first dynamic friction plates 127 are tightly pressed by thefirst pressure disc 129, the power outputted from the electric motor 110(the rotor 112) is transferred to the first gear assembly 120 throughthe first shaft portion 115A of the middle shaft 115 connecting with thefirst clutch 125 and then converted into a first torque, wherein thefirst torque corresponds to the gear ratio of the first gear assembly120. Then, the first torque is further outputted to the differential118T and the power output shaft 117 through a power transmission pathrepresented by arrow signs as indicated in FIG. 5A. Conversely, afterthe first pressure disc 129 is released and returns to the originalposition, the first static friction plates 126 and the first dynamicfriction plates 127 are not connected with each other, therefore thepower outputted from the electric motor 110 will not be transferred tothe middle shaft 115.

Besides, the second dynamic friction plates 137 are furnished on theinner-wall of the common housing 124, and the second dynamic frictionplates 137 match the inner spline TS3 furnished on the common housing124 and extended along an axial direction of the middle shaft 115, suchthat the second dynamic friction plates 137 can move on the inner splineTS3 along the axial direction. The second dynamic friction plates 137synchronically rotate around the middle shaft 115 through the rotationof the common housing 124. Moreover, the second static friction plates136 match the outer spline TS4 furnished on the clutch centering sleeve138 and extended along an axial direction of the middle shaft 115, suchthat the second static friction plates 136 can move on the outer splineTS4 along the axial direction. A second pressure disc 139 is furnishedon the clutch centering sleeve 138. The second pressure disc 139 can bedriven by the hydraulic circuit 140 to move along an axial direction ofthe middle shaft 115 and push the first static friction plates 126 totightly connect with the first dynamic friction plates 127.

Refer to FIG. 5B. When the second piston P2 is pushed on by thehydraulic circuit 140, the second pressure disc 139 furnished on theclutch centering sleeve 138 is activated by the second piston P2 totightly press the second static friction plates 136 and the seconddynamic friction plates 137, such that the second static friction plates136 and the second dynamic friction plates 137 tightly connect with eachother. The second static friction plates 136 are furnished on the clutchcentering sleeve 138, which is further coupled to the second shaftportion 115B of the middle shaft 115. After the second static frictionplates 136 and the second dynamic friction plates 137 are tightlypressed by the second pressure disc 139, the power outputted from theelectric motor 110 (the rotor 112) is transferred to the second gearassembly 130 through the second shaft portion 115B of the middle shaft115 connecting with the second clutch 135 and then converted into asecond torque, wherein the second torque corresponds to the gear ratioof the second gear assembly 130. Then, the second torque is furtheroutputted to the differential 118T and the power output shaft 117through the power transmission path indicated by the arrows of FIG. 5B.Conversely, after the second pressure disc 139 is released, the secondstatic friction plates 136 and the second dynamic friction plates 137are not connected with each other, therefore the power outputted fromthe electric motor 110 will not be transferred to the middle shaft 115.

Refer to FIG. 5C. When the first clutch 125 and the second clutch 135are not driven by the hydraulic circuit 140, the spindle 113 cannotoutput the power to the middle shaft 115. Under such circumstance, therotor 112 of the electric motor 110 is idled and no torque is outputtedto the middle shaft 115, and the electric motor 110 of the electricvehicle maintains at idle speed.

As disclosed above, the clutch controller controls the first clutch 125and the second clutch 135 by using the first piston P1, the secondpiston P2 and the switching of the on/off state of the hydraulic circuit140. That is, when the first static friction plates 126 and the firstdynamic friction plates 127 of the first clutch 125 are pressed tightlyto connect with each other, the second static friction plates 136 andthe second dynamic friction plates 137 of the second clutch 135 separatefrom each other. Conversely, when the first static friction plates 126and the first dynamic friction plates 127 of the first clutch 125separate from each other, the second static friction plates 136 and thesecond dynamic friction plates 137 of the second clutch 135 are pressedtightly to connect with each other. Since the shifting operation of theclutches 125 and 135 is easy and reliable, the neutral gear, which maycause intermittent output of torque and make the vehicle jittering, canbe avoided during the process of shifting gears, and driving comfortwill thus be greatly improved.

Each of the two ports V1 and V2 of the hydraulic circuit 140 has acontrol valve (not illustrated) for controlling the pressure and flow ofthe ports V1 and V2 so as to adjust the internal pressure of thehydraulic cylinder. Given that the two ports V1 and V2 can share onehydraulic cylinder, the inlet direction and the outlet direction can beswitched, and the first piston P1 and the second piston P2 can beintegrated in one piece and furnished within the hydraulic cylinder, onehydraulic circuit 140 would do, and the structure of the transmissioncan be simplified. Since the hydraulic circuit 140 can be connected toone single pump through a pump switch and can further drive the firstclutch 125 and the second clutch 135 by using the one single pump, thehydraulic circuit 140 has a simplified structure, a smaller volume and alighter weight.

The two-speed transmission for an electric vehicle disclosed in aboveembodiments of the disclosure is capable of providing two gear ratios tosatisfy the driver's different requirements of driving the vehicle at ahigh torque or driving the vehicle at a high speed respectively. Thetwo-speed transmission having two clutches has the features of highenergy utilization rate and strong climbing capacity. Additionally, thetwo-speed transmission of the disclosure, having a compact and robuststructure, is light and small and easy to assemble, enhances the powerof the electric vehicle and is beneficiary to the standardization anduse of the electric vehicle.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed embodiments.It is intended that the specification and examples be considered asexemplary only, with a true scope of the disclosure being indicated bythe following claims and their equivalents.

What is claimed is:
 1. A two-speed transmission having two clutches,comprising: an electric motor, comprising a spindle; a middle shaft; afirst clutch and a second clutch coaxially furnished on the middleshaft; a first gear assembly coupled to the first clutch through a firstshaft portion of the middle shaft to generate a first gear ratio; and asecond gear assembly coupled to the second clutch through a second shaftportion of the middle shaft to generate a second gear ratio that isdifferent from the first gear ratio; wherein, when the first clutch isactivated to connect with the first shaft portion, the second clutchseparates from the second shaft portion, so that the electric motoroutputs a first torque corresponding to the first gear ratio through thefirst gear assembly; when the second clutch is activated to connect withthe second shaft portion, the first clutch separates from the firstshaft portion, so that the electric motor outputs a second torquecorresponding to the second gear ratio through the second gear assembly.2. The two-speed transmission according to claim 1, wherein when thefirst clutch and the second clutch are not connected to the first shaftportion and the second shaft portion of the middle shaft respectively, arotor within the electric motor is idled and no torque is outputted tothe middle shaft from the electric motor.
 3. The two-speed transmissionaccording to claim 1, wherein the first gear assembly comprises a firstmain gear furnished on the first shaft portion and a first counter gearmeshed with the first main gear.
 4. The two-speed transmission accordingto claim 3, wherein the second gear assembly comprises a second maingear furnished on the second shaft portion and a second counter gearmeshed with the second main gear.
 5. The two-speed transmissionaccording to claim 4, further comprising a differential and a poweroutput shaft, wherein the first gear assembly or the second gearassembly drives the differential to rotate and transfer the first torqueor the second torque to the power output shaft.
 6. The two-speedtransmission according to claim 1, further comprising a middle shaftgear, wherein the middle shaft gear is furnished on a clutch commonhousing, and the middle shaft gear together with the first clutch andthe second clutch are coaxially furnished on the middle shaft.
 7. Thetwo-speed transmission according to claim 6, further comprising aspindle gear, wherein the spindle gear is meshed with the middle shaftgear.
 8. The two-speed transmission according to claim 1, wherein thefirst clutch comprises a plurality of first static friction platesfurnished on a clutch centering sleeve and a plurality of first dynamicfriction plates staggered with the first static friction plates andneighboring with the first static friction plates to each other.
 9. Thetwo-speed transmission according to claim 8, wherein the first dynamicfriction plates are furnished on an inner-wall of a clutch commonhousing and synchronically rotate around the middle shaft through therotation of the first gear assembly.
 10. The two-speed transmissionaccording to claim 9, wherein the first dynamic friction plates match aninner spline furnished on the clutch common housing and extended alongan axial direction of the middle shaft, such that the first dynamicfriction plates is movable on the inner spline along the axialdirection.
 11. The two-speed transmission according to claim 8, whereinthe first static friction plates match an outer spline furnished on theclutch centering sleeve and extended along an axial direction of themiddle shaft, such that the first static friction plates is movable onthe outer spline along the axial direction.
 12. The two-speedtransmission according to claim 8, wherein a first pressure disc isfurnished on the clutch centering sleeve, and is activated to move alongan axial direction of the middle shaft and tightly press the firststatic friction plates and the first dynamic friction plates, such thatthe first static friction plates and the first dynamic friction platestightly connect with each other.
 13. The two-speed transmissionaccording to claim 12, wherein the first pressure disc is driven in ahydraulic manner.
 14. The two-speed transmission according to claim 1,wherein the second clutch comprises a plurality of second staticfriction plates furnished on a clutch centering sleeve and a pluralityof second dynamic friction plates staggered with the second staticfriction plates and neighboring with the second static friction platesto each other.
 15. The two-speed transmission according to claim 14,wherein the second dynamic friction plates are furnished on aninner-wall of a clutch common housing and synchronically rotate aroundthe middle shaft through the rotation of the second gear assembly. 16.The two-speed transmission according to claim 15, wherein the seconddynamic friction plates match an inner spline furnished on the clutchcommon housing along an axial direction of the middle shaft, such thatthe second dynamic friction plates is movable on the inner spline alongthe axial direction.
 17. The two-speed transmission according to claim14, wherein the second static friction plates match an outer splinefurnished on the clutch centering sleeve and extended along an axialdirection of the middle shaft, such that the second static frictionplates is movable on the outer spline along the axial direction.
 18. Thetwo-speed transmission according to claim 14, wherein a second pressuredisc is furnished on the clutch centering sleeve and is activated tomove along an axial direction of the middle shaft and tightly press thesecond static friction plates and the second dynamic friction plates,such that the second static friction plates and the second dynamicfriction plates tightly connect with each other.
 19. The two-speedtransmission according to claim 18, wherein the second pressure disc isdriven in a hydraulic manner.
 20. The two-speed transmission accordingto claim 1, wherein the first shaft portion and the second shaft portionof the middle shaft are coaxial, and a bearing is furnished between thefirst shaft portion and the second shaft portion.